我正在尝试安装名为devtools的软件包。我运行命令：install.packages("devtools")或install.packages("devtools",dependencies = TRUE)，我得到相同的错误：

Error: package or namespace load failed for ‘gert’:
 .onLoad failed in loadNamespace() for 'gert', details:
  call: NULL
  error: 'as_text' is not an exported object from 'namespace:sys'
Error: loading failed
Execution halted
ERROR: loading failed
* removing ‘/ab/usr/my_user/R/x86_64-pc-linux-gnu-library/3.5/gert’
Warning in install.packages :
  installation of package ‘gert’ had non-zero exit status
ERROR: dependency ‘gert’ is not available for package ‘usethis’
* removing ‘/ab/usr/my_user/R/x86_64-pc-linux-gnu-library/3.5/usethis’
Warning in install.packages :
  installation of package ‘usethis’ had non-zero exit status
ERROR: dependency ‘usethis’ is not available for package ‘devtools’
* removing ‘/ab/usr/my_user/R/x86_64-pc-linux-gnu-library/3.5/devtools’
Warning in install.packages :
  installation of package ‘devtools’ had non-zero exit status

The downloaded source packages are in
    ‘/tmp/Rtmpj3P5T5/downloaded_packages’

字符串
我试着运行install.packages("gert")，得到错误：

Error: package or namespace load failed for ‘gert’:
 .onLoad failed in loadNamespace() for 'gert', details:
  call: NULL
  error: 'as_text' is not an exported object from 'namespace:sys'
Error: loading failed
Execution halted

型
有人有什么想法吗？
下面是一些systemInfo（）：
R版本3.5.2（2018-12-20）平台：x86_64-pc-linux-gnu（64-bit）
我看过类似的问题，评论者/回答者建议关闭和打开Rstudio或重新启动R会话。我试过这些，得到同样的错误。